1. Technical Field
Various embodiments of the present disclosure relate to photomasks used in lithography processes and, more particularly, to photomask blanks, photomasks fabricated using the same, and methods of fabricating photomasks using the same.
2. Related Art
In general, a semiconductor device may include a plurality of patterns disposed on a semiconductor substrate. The patterns may be formed using a photolithography process and an etch process to realize active elements and/or passive elements. The photolithography process may be used to form photoresist patterns. More specifically, the photolithography process may be performed by coating a photoresist material on a target layer to form a photoresist layer, by selectively exposing portions of the photoresist layer to light with a photomask, and by developing the exposed photoresist layer to form the photoresist patterns. The photoresist patterns may be used as etch masks for patterning the target layer. As such, the photomask may be used to transfer predetermined pattern images onto the photoresist layer and may be generally comprised of a transparent substrate and a plurality of transfer patterns.
In the photolithography process, light having a specific wavelength may irradiate a photoresist layer on a wafer through a photomask. In such a case, regions on which light blocking patterns are disposed on the photomask may prevent the light from irradiating the wafer, and only light transmitting regions of the photomask may allow the light to reach the wafer. During the photolithography process, the light blocking patterns may absorb a large amount of optical energy of the light irradiating the photomask, thereby generating heat. The heat may be conducted to the transparent substrate of the photomask, and the transparent substrate may be expanded and deformed due to the heat. The thermal deformation of the transparent substrate may cause a position change of overlay patterns of the photomask. As a result, the thermal deformation of the transparent substrate may lead to an overlay error between the photomask and the wafer.